1. Field of the Invention
The present invention relates generally to the field of propulsion systems for watercraft, such as fishing boats, ski boats, and other pleasure and utility craft. More specifically, the present invention relates to trim control of the propulsion unit in accordance with a defined utility of the watercraft.
2. Description of the Related Art
Recreational watercraft are extremely popular for a variety of uses. Some of the more typical uses may include water skiing, other suitable towing activities, fishing, or simple pleasure riding. All of these activities require the ability of a propulsion system to move the watercraft through the water by providing an adequate amount of thrust.
One conventional approach to providing thrust for a watercraft is the use of an internal combustion engine power source in an outboard or an inboard motor. The motor is typically mounted at the stem of the boat. An outboard motor is typically mounted to the transom of the boat and is drivingly engaged to a prop. Alternatively, an inboard motor is typically housed in the hull of the watercraft while drivingly coupled to a prop located outside the hull. The prop is then driven or rotated by the motor to displace water and thereby to produce the required thrust.
An important component of imparting adequate thrust to the watercraft is trim control. Trim control is, essentially, the alteration of the thrust vector as produced by the prop in an angular manner about a generally horizontal axis. Change in trim allows the motor to more efficiently produce thrust at different stages of operation of the watercraft. For example, as a watercraft is accelerated from a slow pace to a cruising speed, the attitude or angular position of the boat begins to change with respect to the waterline. Likewise, other parameters change such as, for example, engine speed, fuel flow rate, etc. These factors affect the efficiency of the propulsion system as it tries to impart thrust to the watercraft. Thus, it is desirable to alter the thrust vector of the prop as boating conditions change to promote greater efficiency.
Not only do conditions inherent in the performance of the watercraft dictate a change in trim position, but so does the chosen utility of the watercraft. For example, a watercraft pulling a water-skier experiences a different set of operating parameters (i.e., boat speed, engine speed, boat attitude, fuel flow, etc.) than does a watercraft simple cruising with a light load. The chosen utility of the watercraft, including loading conditions and operating preferences, has a great effect on selecting an appropriate or desirable trim position.
Often, the trim position of a propulsion unit is set manually by an operator. Effective manual control of the trim requires careful attention to numerous operating parameters as well as experience with how those operating parameters are affected by a change in trim position. To simplify the process of controlling trim, various attempts have been made to automate the selection of a watercraft""s trim position. The techniques that have been employed often deal with trying to automatically determine an optimal trim position during operation of the watercraft. These techniques can often result in what is known as position hunting. Position hunting is the consequence of an attempt to arrive at an optimal position when the desired position lies between two positions produced by an iterative incremental change. Thus, because the desired position requires a positional change smaller than the defined increment, an endless search for optimization can result. Furthermore, these techniques for optimizing trim are often based upon manufacturing or design decisions. While xe2x80x9coptimalxe2x80x9d is largely an objective standard defined by calculations and empirical data, subjective elements do exist. For example, one operator may consider optimal trim position to produce the best possible boat speed, regardless of the rate of fuel flow. A second operator my believe just the opposite with a desire to expend the least amount of fuel in all situations. Manufacturing and design decisions made in the process of automating trim control for xe2x80x9coptimalxe2x80x9d performance and do not take into account what the individual operator considers as optimal. Nor do the current techniques always consider the differing utility modes that a watercraft may experience along with the fact that each utility mode may redefine what is optimum with regard to trim position.
There is, therefore, a need in the art for a method and system of controlling the trim position of a watercraft""s propulsion unit which is flexible and allows interactivity from the watercraft operator. Such a system and method should be simple to operate and allow trim settings based on either operator selection or on calculation based optimization if desired. The system and method should allow for multiple trim position settings for each utility mode of the watercraft and should allow redefinition of the trim settings with minimum effort.
The invention provides a technique for defining a program for control of the trim position of a propulsion unit mounted on a watercraft. In accordance with the technique, a first utility mode is defined and the watercraft is operated in the defined mode as it would be in normal operation. Multiple trim positions are selected throughout the course of operation in the defined mode. For each selected trim position, an operational parameter of the watercraft is sensed. Multiple values of the same parameter may be sensed and measured for a single trim position. After the parameters have been sensed for each trim position, a correlated data set is created. A correlated data set is saved to a memory device for each selected trim position of the defined utility mode.
The invention also provides a technique for control of the trim position of a propulsion unit, the technique being based upon the program defined in the above mentioned method. In accordance with the technique, the watercraft is again operated in the first utility mode. A current value of the operational parameter is then measured. Having measured the current value of the operational parameter, the correlated data sets are recalled from memory so that the current value may be compared with the stored values in the data sets. The trim position is then selected and set based on the comparison of the current value with those stored in the data set.
The invention also provides a system for controlling the trim position of a propulsion unit mounted on a watercraft. A first sensor is deployed for determination of the trim position. A second sensor is deployed for sensing an operational parameter of the watercraft. A switch is provided for defining a utility mode in which the watercraft will be operated. A processor, such as a microprocessor or other digital circuitry, is coupled to the switch, the first sensor and the second sensor. The processor is adapted to correlate a set of information including the determined position of the propulsion unit with the sensed operational parameter. A memory device is coupled to the processor for storage of the information set allowing subsequent recall of the information.